The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Sie Chin Tjong - One of the best experts on this subject based on the ideXlab platform.
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high temperature creep behavior of tic particulate reinforced ti 6al 4v alloy composite
Acta Materialia, 2002Co-Authors: Z. Y., Rajiv S. Mishra, Sie Chin TjongAbstract:Abstract Tensile creep tests were carried out on a 15 vol% TiC particulate reinforced Ti–6Al–4V alloy composite at 823–923 K. The creep rate data show three regions: a low-Stress region with a Stress Exponent of 2.4–2.6, a medium-Stress region with a Stress Exponent of 4.3–6.1, and a high-Stress region with a Stress Exponent of 8.1–14.3. In the medium-Stress region, the high values of the Stress Exponent ( n =6.1) and activation energy ( Q=310 kJ/mol) at 823 K indicate the presence of threshold Stress. By incorporating the threshold Stress into analysis, all the creep data can be rationalized to a single Stress Exponent of 4.3, which is consistent with the lattice diffusion controlled dislocation climb process in α-Ti. In the low-Stress region, after introducing the threshold Stress into analysis, the creep data fit into a single Stress Exponent of 2, and the activation energy is reduced to be close to that for the lattice diffusion, indicating that the creep mechanism of the composite in the low-Stress region is the grain boundary sliding accommodated by the lattice self-diffusion controlled dislocation climb. In the high-Stress region, an abnormally high Stress Exponent of 8.1–14.3 at 823–873 K is attributed to the occurrence of power-law breakdown.
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High-temperature creep behavior of TiC particulate reinforced Ti–6Al–4V alloy composite
Acta Materialia, 2002Co-Authors: Z. Y., Rajiv S. Mishra, Sie Chin TjongAbstract:Abstract Tensile creep tests were carried out on a 15 vol% TiC particulate reinforced Ti–6Al–4V alloy composite at 823–923 K. The creep rate data show three regions: a low-Stress region with a Stress Exponent of 2.4–2.6, a medium-Stress region with a Stress Exponent of 4.3–6.1, and a high-Stress region with a Stress Exponent of 8.1–14.3. In the medium-Stress region, the high values of the Stress Exponent ( n =6.1) and activation energy ( Q=310 kJ/mol) at 823 K indicate the presence of threshold Stress. By incorporating the threshold Stress into analysis, all the creep data can be rationalized to a single Stress Exponent of 4.3, which is consistent with the lattice diffusion controlled dislocation climb process in α-Ti. In the low-Stress region, after introducing the threshold Stress into analysis, the creep data fit into a single Stress Exponent of 2, and the activation energy is reduced to be close to that for the lattice diffusion, indicating that the creep mechanism of the composite in the low-Stress region is the grain boundary sliding accommodated by the lattice self-diffusion controlled dislocation climb. In the high-Stress region, an abnormally high Stress Exponent of 8.1–14.3 at 823–873 K is attributed to the occurrence of power-law breakdown.
Z. Y. - One of the best experts on this subject based on the ideXlab platform.
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high temperature creep behavior of tic particulate reinforced ti 6al 4v alloy composite
Acta Materialia, 2002Co-Authors: Z. Y., Rajiv S. Mishra, Sie Chin TjongAbstract:Abstract Tensile creep tests were carried out on a 15 vol% TiC particulate reinforced Ti–6Al–4V alloy composite at 823–923 K. The creep rate data show three regions: a low-Stress region with a Stress Exponent of 2.4–2.6, a medium-Stress region with a Stress Exponent of 4.3–6.1, and a high-Stress region with a Stress Exponent of 8.1–14.3. In the medium-Stress region, the high values of the Stress Exponent ( n =6.1) and activation energy ( Q=310 kJ/mol) at 823 K indicate the presence of threshold Stress. By incorporating the threshold Stress into analysis, all the creep data can be rationalized to a single Stress Exponent of 4.3, which is consistent with the lattice diffusion controlled dislocation climb process in α-Ti. In the low-Stress region, after introducing the threshold Stress into analysis, the creep data fit into a single Stress Exponent of 2, and the activation energy is reduced to be close to that for the lattice diffusion, indicating that the creep mechanism of the composite in the low-Stress region is the grain boundary sliding accommodated by the lattice self-diffusion controlled dislocation climb. In the high-Stress region, an abnormally high Stress Exponent of 8.1–14.3 at 823–873 K is attributed to the occurrence of power-law breakdown.
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High-temperature creep behavior of TiC particulate reinforced Ti–6Al–4V alloy composite
Acta Materialia, 2002Co-Authors: Z. Y., Rajiv S. Mishra, Sie Chin TjongAbstract:Abstract Tensile creep tests were carried out on a 15 vol% TiC particulate reinforced Ti–6Al–4V alloy composite at 823–923 K. The creep rate data show three regions: a low-Stress region with a Stress Exponent of 2.4–2.6, a medium-Stress region with a Stress Exponent of 4.3–6.1, and a high-Stress region with a Stress Exponent of 8.1–14.3. In the medium-Stress region, the high values of the Stress Exponent ( n =6.1) and activation energy ( Q=310 kJ/mol) at 823 K indicate the presence of threshold Stress. By incorporating the threshold Stress into analysis, all the creep data can be rationalized to a single Stress Exponent of 4.3, which is consistent with the lattice diffusion controlled dislocation climb process in α-Ti. In the low-Stress region, after introducing the threshold Stress into analysis, the creep data fit into a single Stress Exponent of 2, and the activation energy is reduced to be close to that for the lattice diffusion, indicating that the creep mechanism of the composite in the low-Stress region is the grain boundary sliding accommodated by the lattice self-diffusion controlled dislocation climb. In the high-Stress region, an abnormally high Stress Exponent of 8.1–14.3 at 823–873 K is attributed to the occurrence of power-law breakdown.
Tatsuo Kumagai - One of the best experts on this subject based on the ideXlab platform.
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estimation of Stress Exponent and activation energy for rapid densification of 8 mol yttria stabilized zirconia powder
Journal of the American Ceramic Society, 2013Co-Authors: Tatsuo KumagaiAbstract:The rapid densification behavior of 8 mol% Y2O3-stabilized ZrO2 polycrystalline (8Y-SZP) powder compacts at the initial stage of pressure sintering (relative density (ρ·) below 0.92) has been investigated using an electric current-activated/assisted sintering (ECAS) system. Data points corresponding to a fixed heating rate were extracted from the densification rate (ρ·) versus ρ and ρ· versus temperature (T) curves. These curves were obtained experimentally by consolidation at a fixed current. Under fixed current ECAS, the heating rate (T·) decreases continuously over sintering time. Using a quasi- constant heating rate (CHR) method, data points were extracted to plot ρ· vs. ρ, ρ· vs. T, and ρ vs. T curves at a fixed T·. The Stress Exponent (n), estimated from a log-log plot of grain size (d)-corrected ρ·/ρ and effective Stress (σeff) at 1300–1400 K, shows an almost constant value of 1. In addition, the activation energy (Q) for rapid densification, estimated from an Arrhenius plot of d-corrected ρ·/ρ also shows an almost constant value of 350 kJ/mol, which is considerably lower than the previously reported value of the activation energy for Zr4+ lattice diffusion of about 440 kJ/mol. These results suggest that rapid densification of 8Y-SZP by ECAS seems to proceed by diffusional creep controlled by grain-boundary diffusion of Zr4+ ions.
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Estimation of Stress Exponent and Activation Energy for Rapid Densification of 8 mol% Yttria‐Stabilized Zirconia Powder
Journal of the American Ceramic Society, 2012Co-Authors: Tatsuo KumagaiAbstract:The rapid densification behavior of 8 mol% Y2O3-stabilized ZrO2 polycrystalline (8Y-SZP) powder compacts at the initial stage of pressure sintering (relative density (ρ·) below 0.92) has been investigated using an electric current-activated/assisted sintering (ECAS) system. Data points corresponding to a fixed heating rate were extracted from the densification rate (ρ·) versus ρ and ρ· versus temperature (T) curves. These curves were obtained experimentally by consolidation at a fixed current. Under fixed current ECAS, the heating rate (T·) decreases continuously over sintering time. Using a quasi- constant heating rate (CHR) method, data points were extracted to plot ρ· vs. ρ, ρ· vs. T, and ρ vs. T curves at a fixed T·. The Stress Exponent (n), estimated from a log-log plot of grain size (d)-corrected ρ·/ρ and effective Stress (σeff) at 1300–1400 K, shows an almost constant value of 1. In addition, the activation energy (Q) for rapid densification, estimated from an Arrhenius plot of d-corrected ρ·/ρ also shows an almost constant value of 350 kJ/mol, which is considerably lower than the previously reported value of the activation energy for Zr4+ lattice diffusion of about 440 kJ/mol. These results suggest that rapid densification of 8Y-SZP by ECAS seems to proceed by diffusional creep controlled by grain-boundary diffusion of Zr4+ ions.
Rajiv S. Mishra - One of the best experts on this subject based on the ideXlab platform.
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high temperature creep behavior of tic particulate reinforced ti 6al 4v alloy composite
Acta Materialia, 2002Co-Authors: Z. Y., Rajiv S. Mishra, Sie Chin TjongAbstract:Abstract Tensile creep tests were carried out on a 15 vol% TiC particulate reinforced Ti–6Al–4V alloy composite at 823–923 K. The creep rate data show three regions: a low-Stress region with a Stress Exponent of 2.4–2.6, a medium-Stress region with a Stress Exponent of 4.3–6.1, and a high-Stress region with a Stress Exponent of 8.1–14.3. In the medium-Stress region, the high values of the Stress Exponent ( n =6.1) and activation energy ( Q=310 kJ/mol) at 823 K indicate the presence of threshold Stress. By incorporating the threshold Stress into analysis, all the creep data can be rationalized to a single Stress Exponent of 4.3, which is consistent with the lattice diffusion controlled dislocation climb process in α-Ti. In the low-Stress region, after introducing the threshold Stress into analysis, the creep data fit into a single Stress Exponent of 2, and the activation energy is reduced to be close to that for the lattice diffusion, indicating that the creep mechanism of the composite in the low-Stress region is the grain boundary sliding accommodated by the lattice self-diffusion controlled dislocation climb. In the high-Stress region, an abnormally high Stress Exponent of 8.1–14.3 at 823–873 K is attributed to the occurrence of power-law breakdown.
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High-temperature creep behavior of TiC particulate reinforced Ti–6Al–4V alloy composite
Acta Materialia, 2002Co-Authors: Z. Y., Rajiv S. Mishra, Sie Chin TjongAbstract:Abstract Tensile creep tests were carried out on a 15 vol% TiC particulate reinforced Ti–6Al–4V alloy composite at 823–923 K. The creep rate data show three regions: a low-Stress region with a Stress Exponent of 2.4–2.6, a medium-Stress region with a Stress Exponent of 4.3–6.1, and a high-Stress region with a Stress Exponent of 8.1–14.3. In the medium-Stress region, the high values of the Stress Exponent ( n =6.1) and activation energy ( Q=310 kJ/mol) at 823 K indicate the presence of threshold Stress. By incorporating the threshold Stress into analysis, all the creep data can be rationalized to a single Stress Exponent of 4.3, which is consistent with the lattice diffusion controlled dislocation climb process in α-Ti. In the low-Stress region, after introducing the threshold Stress into analysis, the creep data fit into a single Stress Exponent of 2, and the activation energy is reduced to be close to that for the lattice diffusion, indicating that the creep mechanism of the composite in the low-Stress region is the grain boundary sliding accommodated by the lattice self-diffusion controlled dislocation climb. In the high-Stress region, an abnormally high Stress Exponent of 8.1–14.3 at 823–873 K is attributed to the occurrence of power-law breakdown.
Nirmal K. Sinha - One of the best experts on this subject based on the ideXlab platform.
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Stress Exponent and primary creep parameters using single specimen and strain relaxation and recovery test
Materials Science and Engineering: A, 2009Co-Authors: Nirmal K. SinhaAbstract:Strain relaxation and recovery test (SRRT), requiring one specimen and viscous (permanent) strain, ɛv (≤0.001 per test) on full unloading during primary creep, is presented with results on gas-turbine engine materials: Ti-6246 at 600 °C, Discaloy at 500 °C, IN-738LC at 850 °C and Waspaloy at 732 °C. It is shown that a ‘steady-state’ in irreversible viscous flow develops during primary creep; the shape of the creep curve is controlled by time-dependent reversible delayed elastic (anelastic) response. The average viscous strain rate during primary-creep, e˙v(av)(=ev/tSR) for load duration, tSR and corresponding ɛv can be used for the determination of the Stress Exponent, nv for viscous flow. It is shown that the value of nv for primary-creep is comparable to the Stress Exponent, nmin for minimum creep rate. Using a single specimen, SRRTs also allow determinations of Young's modulus, Stress Exponent, s for delayed-elasticity (anelasticity), about one-third to fourth of nv, and other parameters for the constitutive equation for primary creep—strictly before creep enhancement due to the onset of microcracking activities. Short-term and long-term SRRT data on Waspaloy indicated that the creep strain at minimum creep rate consists of a significant amount of recoverable strain (32% at 450 MPa and 38% at 650 MPa).
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Viscous and delayed-elastic deformation during primary creep-using strain relaxation and recovery test
Scripta Materialia, 2003Co-Authors: Nirmal K. SinhaAbstract:Abstract Closed-loop controlled constant-Stress ‘strain relaxation and recovery tests’ were performed on a titanium-based alloy at 0.45 T m to examine primary creep. Viscous (permanent) strain rate was found to be constant, obeying power-law with Stress Exponent of 4.0. The deceleration in creep rate is attributed to recoverable delayed-elastic response obeying logarithmic time dependence with a Stress Exponent of 1.2.
